Surface treating machine



July 7; 1959 I. JEPSON 2,893,174

SURFACE TREATING MACHINE Filed March '7. 1956 r 3 Sheets-Sheet 1 July 7, 1959 JEPSQN 2,893,174

SURFACE TREATING MACHINE Filed March 7, 1956 5 Sheets-Sheet 2 July 7, 1959 l. JEPSON SURFACE TREATING MACHINE Sheets-Sheet 3 Filed March 7, 1956 m m m m r at a convenient place.

- SURFACE TREATING MACHINE Ivar Jepson, Oak Park, III., assignor to Sunbeam Corporation, Chicago, 111., a corporation of Illinois Application March 7, 1956,-Serial No. 569,990

l 4 Claims. (01. 51-170) The presentinvention relates to surface treating machines, and more particularly to power driven devices or .tools adapted to be" manipulated over a surface to be treated forsanding, grinding, polishing, bufiing, or otherwise treating the same. Since the most common use of such devices is with respect to sanding such surface to be treated, it is usual to refer to such surfacing machines as power sanders, although obviously they can be used for other than sanding opertaions. In the ensuing description and claims when reference is made to a power sander, it is intended to connote broadly surface treating devices.

' In surface treating machines, of which perhaps the most important is a sanding machine, the portable electric sander has become very popular in recent years. There is hardly an adult person today who has not had occasion to use a sander in some form or other for treating a surface whether it be the surface of a piece of furnient invention is particularly concerned with an improved orbital sander. An orbital sander is one in which the base plate or shoe supporting the sandpaper or other material for affecting the surface to be treated is caused to move in a positive fashion around the orbit of a circle, and hence the name orbital sander. Such sanders have been available on the market heretofore, but they have had numerous shortcomings. It would be desirable to provide a portable electric sander or surface treating machine which is capable of withstanding extensive use, such as many hours of continuous use. Moreover, the orbital action of the sander should be steady and balanced with a minimum of vibration. Such a sander should be very light'in weight and have perfect balance, so that it is comfortable for the operator to use, particularly when performing such functions as sanding fiat work, side walls or ceilings. The control of the motor should be located The device should require substantially no care other than occasional lubrication.

A surface treating machine such as an electric sander requires simple and readily actuatable means for releasing and securing the sandpaper to the machine. In any particular sanding operation it may be desirable to start the surface treating machine with a course sandpaper, followed by a medium and then a fine paper, and this action may be followed by a waxing or polishing operation using the same surface treating machine. Obviously,

this requires a mechanism for quickly attaching and re- United States PatentO it would be desirable to provide a locking device which clamps any form of abrasive such as sandpaper tightly thereto regardless of the thickness of the abrasive paper and without the requirement of any tools.

In an orbital power sander, it is necessary to convert rotary motion developed by an electric motor or other prime mover to oscillating'motion by an eccentric or similar device. The forces transmitted to perform a satisfactory sanding operation are substantial and the means of accomplishing this in prior art arrangements have not been satisfactory to insure long years of troublefree service. It would be. desirable to provide 'an 'arrangement in which the forces which are transmitted through pulleys, bearings and the like are transmitted directly so as to cause a minimum of wear.

Accordingly, it is an object of the present invention to provide a new and improved surface treating machine.

It is another object of the present invention to provide a portable electric sander of the orbital type which is light in weight and embodies substantially perfect balance. I q

It is a further object of the present invention to provide a surface treating machine having the desirable features enumerated above. t

It is another object of the present invention to provide a surface treating machine of the type in which. a base plate moves through an orbital path in which improved means are provided for transferring the force causing such orbital movement of said base plate.

Still another object of the present invention resides in an electric sander having improved clamping means for permitting quick removal and subsequent reattachment of the abrasive paper, which means will securely hold such paper regardless of the thicknesspand which releasing and locking means may be actuated without the use of any tools. A 3 Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularityvin the claims annexed to and forming apart of. this specification. V

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

Fig. l is a perspective view of a surface treating machine embodying the present invention;

Fig. 2 is a greatly enlarged side elevational sectional view taken substantially along line 2-2 of Fig. 1, with the sandpaper removed therefrom, but showing certain portions in full lines and certain other portions in section in order more clearly to illustrate the present invention;

Fig. 3 is a sectional view taken on linev 3-3 of Fig. 2, assumingthat Fig. 2 shows the complete structure except for the sandpaper; r

Fig. 4 is a sectional view taken on line 44 of Fig. 2, again assuming that Fig. 2 shows the complete structure.

Fig. 5 is a fragmentary sectional view taken on line 5--5 of Fig. 4;

Fig. 6 is a perspective view of the damping pad and stamping bracket shown in section in Fig. 5; I

Fig. 7 is a fragmentary sectional view taken on line 7-7 of Fig. 2, assuming that Fig. 2 shows the complete structure; and

Figs. 8, 9 and 10 are schematic, somewhat diagrammatic perspective views, illustrating the method of re placing the sandpaper of the surface treating machine of the present invention.

Briefly, the present invention is concerned with a surface treating machine comprising a vertically disposed motor having its shaft extending into somewhat recac nefcornprlses"abase platell which should ed n an orbital pathso that"when'fa suitable such I tipapfer jorfthe "like isfsecured theresanding or the; surface treating operation can 'be plishedfin espo s 'to'thefmovernent of the base atefabout'itsorbital path, The base platell issecured ijto'fafsuitablejbase' member 12' by, resilient means generly designatedjas "13g and described in greater detail hereinafter. "Secured to the-base member 12 is a suitable motor housing 14 within which is contained a suitable yerfor motor inleans generallv'indicatedas an e c rc motor "15. 'Ah'andle-*16'*secured to the motor p errnits the operator to manipulate the surmac ire-1: 8.. t ng ni'or'e in detail the genleral "construction j efation of the surface treating machine 10, consrderatibnis firstf given ;to the base "plate or shoe '11, which is the'p ort ion'of the surface treating-machine 10 that s"actiiated for 'iriovement in an orbital path to andingjor other surfacetreating operation. 'As st s nin Fig s. '2and'3'of'the drawings, the base fplate- 1'1; sa rectangular plate formed of relatively'heavy metal marinara size to accommodatesandpaper or iiither surfacetre ating material available on the market. Th iz of the rectangular sheet will, of course, depend I jthe inio'ton'which" it-is-desir ed' to use (to ctua tethe' same. Ina surface treating'machine 'Ibuil n accordancewith the present invention, the base 1p llwas of' the order"of between three'and four 'inchesin"width,'and between six and eight" inches in length. 'Iheparticular size of the base plate, however, fisjunimportant so far asthepresent invention is concerned. In order to provide a somewhat resilient cushion or backing for'a" surface treating element, such as an 'abrasive coated material/indicated the sandpaper 17, fwhich 'isto be secured} to the 'b ase plate 11, there'prefer- T bly 'issecured to the lower side} of the base plate- '11, F viewed: inFigPZ 'off the drawings, j a padlikeinember 318 'whickmay be formed of pressed felt, rubber, or simila r resilient'materi'al. pad 18*is of 'sufiicient thickness to provide a resilientbacking for any element suitable for engaging the worksurface to'be treated, whether it bean abrasive coated material or thelike. As best shownin Fig. 1 of the. drawings, the sandpaper 17 is fjse'cured' o the baseplate 1 1 in a manner to be described "here nafter; so that the active surface of the sandpaper 17is disposed downwardly asviewedin Fig. 1, and the o therside of the sandpaperl? rests against the resilient pad18. The" resilient pad 18' may befse'cur'ed to the b p satrenvay thereto. "For'the purpose or actuating the'ba'se plate 11 and the associated element attached thereto for performing ace. treating operatio a bearing housing or beargigniouintingineans '19'is secured to the base plate Ill "'on' the sideoppositethe side to which 'the pad 13 is secured, which I essentially v :ornp rises a: cylindrical mem- -!e .ns t;1 w nn We d-p wis secured n ?5g1 e p rtiq j 9 hebfl er eh s be ing housing 19 is adapted to support therein a suitable baseplatef infany 'siiitable manner. For example, it

.4 elongated bearing or needle bearing 21, Preferably, an oil wick 22 and a suitable retainer 23 are provided at the upper end of the bearing housing 19 which is open to insure proper lubrication of the needle bearing 21. In a device built in accordance with the present invention, the bearing housing 19 was of the order of an inch in length, but/obviously, it might have other dimensions. It moreoverhad 'a'diameter of the order ofbetween an inch and an inch and a half.

To permit readyattachm'ent and detachment of the sandpaper or other element to be secured to the base plate 11, thetwo-ends of-the base-plate-ll are deformed slightly to define a pair of upwardly directed flanges 11a and 11b which "act as "clamping surfaces against which the material such as sandpaper may be frictionally pressed or clamped to secure the same in position. The clamping surface defined by the element 11b might be considered the forward clamping surface, while the clamping surface defined by theelement II'a'mi'ght be conwhere the surface t'r'ating machine 10 is'a' sarid'er. As illustrated, the locking a'rms25 each comprise a U-shaped portion, the 'bight 25a of which cooperates with the associated one ofthe flanges 11a or 11b to clampone end of the surface treating'element such"as"17 'thereto. *The legs] 'of the U'-shaped portion ofeach 'lockingfarm 25,

which'b'etw een them define the bight portion 2-5a, ter- "minate in lateral-projections 25band 25c whichact as trunni'ons' preferably supported in trunnion supports llc, whichmay be formcd'fromtabs integral with'the base plate 11. A pair of trunnion supports 11c are provided at eachfendof the base" plate 5 11, To manipulate the sandpaper: locking arm" 25, *ohe of the trunnions such as "25b jof eachlocking"arm' '25 is" provided'with an exten- "sio'n25d projecting in manner generally perpendicular to the axis of the'trunnion' to definea handle whereby the operator may manipulatethe loc'kinga'rm 25. The end of "this handleportionfdesignated'as ZSe, is flattened to pro- 'vide an angularly disposed' surface Which may readily be grasped by the thumb'of the operator to manipulate the same. The base plate 11 is further provided witha pair of hook-shaped tabs 11d and 11:2 'disposed' on opposite sides of the base plate lladjacent the portions 25d of the lockingarms'25 so that theseportions' may be hooked under the locking tabs lld'of I le -'toholdthelocking arms in sandpaper clamping relationship. Eachof these lockirig arms 25' ispre'ferably formed of resilient 'steelfwire jor the like andis desig iid solhfh'v'hn' lriifid from the dotted 'lineposition shown in Fig.2 of the drawings to the solidline position'by'rotation about the trunnions 25c and ZSb, the bight of the U'-'sh'aped clamping portion 25a engages the associated clamping surface defined by fiaii ge 11a or' 11b before the arm portion 25d thereof'engages the base plate 11 Continued movement 'of thea'rm poi'tion'ZSdbf eachlo'ckingarmfso that it eventually engages the locking tab 11d or lle; will cause 'a'distortion of the'big'ht 25a of the U-shaped portionto I insureproper' clampi'rigof any mater'ial,reg'ardless ofhow thin, between this bight portion 25aand"the clamping "surface on the flange 11a or llb, as the case may be. In view of the detailed description-of 'the' lo'clring arms 25, it will readily be" appreciated that-an el'ement can be secured to the base plate ll-in a'very'simp1emanner. u As best shown in Fig. 8 of -the d'rawings, thelocking arms 25 may be released by unhooking the corresponding-arni portions'25d by first pressing down on these' arm portions and then pulling" slightly-sidewaysto free the corresponding manipulating arms 25d from ;the hooked portions such as 11 1 or He. The surface treating mabetween the flanges 11a and 11b and the corresponding cooperating portions of the associated locking "arms 25. When this has been done, the sander or surface treating machine can beset down in the manner indicatedin Fig. of the drawings and the clamping means secured in the manner shown in Figs. 1 and 10 of the drawings, whereby the sandpaper such as 17 is securely locked thereto. It will be appreciated that this can be accomplished in a satisfactory manner regardless of the thickness of the sandpaper 17. Furthermore, this can be accomplished without the use of any tools.

For the purpose of supporting the base plate 11 for relative movement with respect to a suitable support, and further for the purpose of housing some of the power transmitting mechanism, the base member 12 is provided, which, in an embodiment built in accordance with the present invention, had a rectangular configuration slightly smaller than the base plate 11. Effectively, the base member 12 is illustrated as an inverted rectangular box completely open at the bottom, with the open end overlying the base plate 11. In order to secure the base plate 11 to the base member 12 in a manner-to permit the necessary orbital movement of the base plate 11, there I are provided resilient supporting columns 13 which extend between the base plate 11 and the base member 12.

As illustrated, four columns 13 are provided, one adjacent each corner of the respective base member 12 and base plate 11. As best shown in Fig. 2 of the drawings, each of the columns 13 is preferably formed of a resilient material, such as a rubber column, to each end of which is secured a threaded member designated specifically as 13a and 13b in Fig. 2 of the drawings. These threaded members 13a and 13b may be shaped as bolts with-the heads thereof secured adhesively or molded directly to the ends of the resilient column 13. As illustrated in the drawings, the lower ends of the resilient columns 13 abut against the top of the base plate 11 with the threaded portion of the elements 13b extending through suitable openings defined in the base plate 11. Suitable nuts 28 hold the resilient columns 13 in asnum or the like, there are provided a plurality of inserts 31 press fitted into suitable openings in the top wall of the base member 12. vThese inserts are pro- .videdwith tapped openings to receive the threaded portions of the members 13a. Obviously, the upper ends of the resilient columns 13 are first secured to the base member 12, whereupon the lower ends 13b may then be secured to the base plate 11 in an obvious manner. With this arrangement the base plate 11 is secured to the base member 12 through the resilient columns 13 which will permit limited relative movement between the base member 12 and the base plate 11 to the extent required for orbital movement to perform a satisfactory surface treating operation. In a device built in accordance with the present invention, the resilient columns 13 had a length of between one and two inches, and had a diameter of between one half and three quarters of an inch.

The base member 12 and the motor housing 14 referred to above are effectively a unitary structure insofar as the operation of the device is concerned. However, for assembly purposes, they are separate elements and the housing 14 is preferably also a die casting of lightweight metal such as aluminum. For the purpose of uniting the motor housing 14 and the base member 12 to form a rigid structure, the top of .the base member 12 is preferably provided'with a plurality of spacer projections 34, best shown in Figs. 2 and 4 of the drawings, which are adapted to engage the lower end of the motor housing 14 at the four corners thereof, thereby to space the motor housing slightly from the base member 12 and provide air passageways such as 35 between the motor housing 14 and the base member 12, and moreover between the spacer members 34. 3

For the purpose of accurately positioning the motor housing 14, which is of generally rectangular configuration at the lower end thereof, with respect to the base member 12, each of the spacers 34 is provided with a pair of projections 34a. With this arrangement, two of these projections 34a engage the inside of each of the four wall surfaces defining the motor housing 14. Thus, the spacer members 34'properly orientate the motor housing 14 and the base member 12 with respect to the vertical direction, and the projections 34a properly orientate these members 12 and 14 with respect to the horizontal plane when the surface treating device '10 is in the position shown in Fig. 2 of the drawings. For the purpose of securing the motor housing 14 to the base member 12, the former is provided interiorly with a plurality of spaced vertically extending ribs 14a integrally joined to'the interior of the housing 14, which ribs have spaced openings 36 at thelower ends thereof to receive fastening means 37 which extend through the top wall of the base member 12. t

For the purpose of accommodating a prime mover specifically designated as an electric motor 15, means are provided to hold the field structure of such a motor designated as 38 in assembled relationship with the housing 14 which defines therein the motor chamber 40. The armature 41 of the motor is provided with the conventional armature shaft 42, one end of which is journalled in a bearing 43 suitably supported in one end of the housing 14 which is indicated as a substantially closed end. The other end of the motor shaft 42 is journalled in a bearing 44 supported in the base member 12 which is provided with a suitable opening to permit the lower end of the shaft 42 to extend into a mechanism chamber 44 defined within the base member 12 above the base plate 11 when the device is positioned in the manner shown in Fig. 2 of the drawings. a

To insure cooling of the motor 15, there is preferably provided a fan 46 secured to the motor shaft 42 at the lower end of the motor chamber 40 above the base member 12. A suitable fan shroud 47 surrounds the fan 46 and is preferably held in assembled relationship with-the base member 12 and the motor housing 14 by the fastening means 37, which may extend through notches or openings defined in the shroud 47. To preclude the drawing of sanding dust into the motor housing 14, preferably the upper end of the housing, as best shown in Fig. 1 of the drawings, is provided with a plurality of air inlet openings 49 whereby the fan 46 may cause the air to flow through the chamber 40 to cool the motor 15 and out through the passageways 35. If desired, the top of the base member 12 immediately beneath the motor-housing 14 may also be provided with a plurality of openings (not shown) for the flow of motor cooling air. This air flow will tend .to blow the sanding dust away from the motor housing 14.

In order to lubricate the bearing 43, the motor housing 14 is provided with an oil passageway 51 through which oil may be supplied to the bearing 43. To insure lubrication of the bearing 44, the upper surface of the base member 12 is preferably provided with a recess 52 for receiving a suitable oil wick 53. The oil wick 53 is held in position by a suitable combined bearing and oil wick retainer 54 secured to base member 12 by fastening means 55. Thus, retainer 54 holds the bearing 44 assembled to the base member 12, so that when the fastening means 37 are removed, the motor armature 41 remains assembled with the base member 12, and the motor shaft 42 pulls free of the bearing 43, which bear he'ldflin position in 7 I a the motor'housing l tiby a suitablebearing retainer member 56 heldin position by fastening means not shown secured to motor. housing l tandsimilar to the fastening means 55.

To-cau'se the base plate ll'to-move in an orbital path in response to rotation of thearmatureshaft 42, there is secured-to the lower end of the armature shaft 42 within mechanism chamber 44 atoothed pulley "57 for accommodating the conventional endless belt 58 having suitablepprojections on the inner pulleyengaging surfaces thereof. -Such driving belts are commonly referred to as timing belts and are capableof transmitting a substantial force, without slippage, between a drivingand a .drivempulley. The toothed pulley 57 is, of course, the drivingpulley. t

{In accordance with thepresent invention, a combined driven pulley and counterweight mechanism 59 is provided which has secured thereto by fastening means. 60

-a sleevelike bearing housing" 61. The portion of the combined element 59 exclusive of the counterweight is designated as 59a, while the counterweight portionis designatedas 59b. Theportion 59a andthe bearing-housing -61 secured thereto might be termed a rotatable drive member which has defined'therein anopening 62 which is so disposedwith respect to the combined pulley and counterweight 59 that the exterior-ofthe sleevelike bearhousing 61 houses a. pair ofneedle bearing units 64 and '65 which together -define selongated bearing means.

;Moreover, the eccentrically disposed exterior surface of thebearinghousing-614s caused to move in an orbital .path andis'adapted to bereceived within the bearing housing 19 secured to the base plate 11, and effectively is journalled within'the needle bearings 21 contained therein. As was mentioned above, the'pulley portion ofthe combined pulley and counterweight mechanism 59 is designated at 59a and comprises teeth to cooperate with the toothed belt 58. Actually, a-substantial speed reductionis obtained by 'virtue of the belt and pulley arrangement described-above, since the pulley portion 59a is substantially larger in diameter than is the toothed .pulley 57. The counterweight portion'59b of the combinedpulley 'and counterweight 59 balances the'unbal- 'ancedforces produced byvirtue of eccentricity of the hearing housing-having'the opening'62 therein :as well as the unbalanced forcscreated by virtue of the base platell.

In accordance with the present invention, the unit comprising the'combined pulley and-counterweight 59 and the bearing housing 61 secured thereto by the fastening means 60 are arranged to define, on the underside thereof as-viewed in Figs. '2 and 3 of the drawings, a central annular're'ce'ss 67 eccentric with respect to the recess to'the driven'member through the other end of the shaft. With thepresent arrangement not only is a compact structureprovided, but the forces are transmitted-in a direct manner with a minimum of vibration. The counterweight portion 59b is effectively disposed to trans- 8 mit its force radially along a line substantially atthe center of the telescoped members 19 and 61.

Toinsure proper .lubrication of the needle .bearings'64 and 165, the stationary shaft 63 is preferably provided therein with an axial oil passageway 70:: connected to a radial passageway 70b clearly shown in .Figs. 2 Land '3 of the drawings. A suitable removable cover 71 normally closes the upper end of the axial passageway 70a. Any suitable means for securingthe bearing shaft 63 to the base member 12 may be employed. vAs illushated, the bearing shaft 63 .is in the form of a shouldered bolt having a head 63a at the lower end thereof .tohold the combinedpulley andcounterweight 59 and associated bearing housing '61 assembled thereto. The upper end of the bearingshaft 63 is ofreduced cross section and threaded to-extend through an opening 72.in .base member l-Zand-secured thereto by a nut 73. It will .beapparent that rotation of the motor shaft 42 will cause the'base plate 11 to move in an orbital path. In a .device built in accordance with thepresent invention, such movement was an eccentric movement between a .quarter inch and a half inch.

So that the operator may readily manipulate the surface treating machine 10, the motor housing -14preferably includes an integral extension 14b which, together with a removablecooperating handle member 16a, defines -.the handle .16. The removable handle member 1 6a'is secured to the extension 14b'by suitable fastening means such as 74, and is removable to permit access to the electrical control circuit disposed within a hollow recess orchamber designated as 75, defined within the handle portion. This'recess is adapted to accommodate a suitable switch 76 connected in the motor'circuit in the conventional manner. For the purpose of supporting the switch 76, it preferably is provided with a mounting 'plate 77, which plate is adapted to be received within cooperating grooves 78 and 79 defined in the handle-lportions 14b and 16a respectively. Thus, it is merelymecessary to ,iPOSltlOIl the switch 76 within the recess 75 so that one edge of the plate 77 is disposed within the groove 78 in extension 14b. The handle member 16a'is then assembled so'that the opposite edge of switch-plate 77 is disposed in groove 79. Effectively the grooves 78 and 79 are defined in theedges of an opening 80 provided in the handle 16, one half "of the opening'being defined in each handle portion 14b and 16a. This opening 80, which is at the upper portion of the handle adjacent theimotor housing 14 andadjacent the normal place where the operator will keep his :thumb, permitsa manually actuatable switch knob 81 to extend outside the handle 16 so'that it can readily be actuated by the operator. Preferably, the switch plate 77 .in- 'cludes suitable indicia on the'upper surface, as'viewed in Fig. 2, which indicates the operating condition of the switch 76. The manually actuatable switch knob 81 may be'constructed so asto obscure the indicia which does not properly describe the particular operating condition of the switch 76.

In order to-supply the necessary'electricalenergy for the-motor 15,:'the surface treating device 10 is'provided 'with the conventional power cord 82, which preferably extends into the chamber 75 in the handle 16 through an opening 83. A conventional 'cordsleeve 84 preferably surrounds the power cord 32 at the entrance opening 83 andincludes an enlargement 84a which is adapted to be received within-a suitable recess'85 defined in the handle 16. The 'sizes of 'the'recess 85 and the'enlargement'84a are such as to insure that the cord sleeve 84 is clamped into tightly gripping relationship with the'power cord" 82 when the removable handle portion 16a is secured to the handle portion 1411 by the fastening means 74. This, then, affords a suitable strain relief.

Topermit two-hand operation, thesurface treatingdevice =10 includes a knob 86 secured as by a screw'87 to the upper front of the motor housing 14. Preferably, the

knob 86 is formed of a suitable molded material and may be molded directly to the screw 87. This knob may readily be removed from the surface treating machine 10 when sanding in close quarters, such as corners or the like, and may easily be attached to the sander to permit more satisfactory operation.

In view of the detailed description included above, the operation of the surface treating machine of the present invention, which is particularly well adapted for use as a portable power sander, will readily be understood by those skilled in the art. When power is supplied to the motor 15 upon sliding the switch knob 81 of switch 76 to the on position, rotation of the combined pulley and counterweight 59 occurs, thus causing the eccentric bearing housing 61 to rotate about the bearing shaft 63. Such eccentric movement of bearing housing 61 causes a force to be transmitted directly to the base plate 11 which in turn is moved through an orbital path.

If desired, a suitable vibration damping means may be employed in connection with the base member 12. In one embodiment built in accordance with the present invention, the interior of the vertically disposed walls of the base member 12, as viewed in Fig. 2 of the drawings, were lined with a layer of pressed felt or the like. However, in the preferred embodiment built in accordance with the present invention, as best shown in Figs. 5 and 6 of the drawings, a small damping pad 91 is held to the interior surface of the vertical walls defining the base member 12 by a suitable damping bracket 92, which bracket was held to the base member 12 by one of the fastening means 37 which hold the motor housing 14 to the base member 12. It will be appreciated that if one touched a finger to a conventional bell, a considerable damping action would ensue, and the damping pad 91 functions in this manner.

While there has been illustrated and described what is at present believed to be a preferred embodiment of the present invention, numerous changes and modifications will readily occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A surface treating machine comprising a base member, a base plate spaced from and resiliently supported from said member, motor means incuding a shaft journalled in said base member, a rotatable drive member driven by said shaft and having a first recess centered relative to the periphery of said drive member and opening on at least one face of said drive member, said drive member also having a second recess eccentric relative to said first recess and opening on the opposite face of said drive member from said one face, said recesses longitudinally overlapping one another, first bearing mounting means fixed to said base member and extending into said first recess, second bearing mounting means fixed to said base plate and extending into said second recess, first elongated bearing means positioned in said first recess and mounting said rotatable member rotatably on said first bearing mounting means, and second elongated bearing means mounted in said second recess and mounting said rotatable member rotatably on said second bearing mounting means, said first bearing means and said second bearing means overlapping one another to an extent such that the center of forces transmitted from said second bearing means is between the ends of said first bearing means.

2. The surface treating machine of claim 1 wherein said base member is a rectangular boxlike member open at the bottom with said base plate supported adjacent said open end thereof, and wherein the resilient support for said base plate comprises a plurality of columns of rubberlike material disposed between said base member and base plate within said boxlike member.

3. The surface treating machine of claim 1 wherein vibration damping means are associated with said base member.

4. The combination of claim 1 wherein a counterweight is secured to said rotatable drive member to balance the unbalanced forces created by virtue of the eccentric recess, said counterweight being a mass effectively disposed along the line of eifective force transmission between said second bearing mounting means and said rotatable drive member.

References Cited in the file of this patent UNITED STATES PATENTS 2,683,336 Scace July 13, 1954 2,697,897 Dickinson Dec. 28, 1954 2,697,898 Osman Dec. 28, 1954 2,751,725 Champayne June 26, 1956 2,764,852 Emmons Oct. 2, 1956 

